Parthenium hysterophorus (P.H.) is a member of the Asteraceae long thought to be non-allergenic. Recent evidence has indicated, however, that the pollen from this weed is airborne in large quantities and that a significant proportion of the atopic population in the United States Gulf coast from Texas to Florida (population more than 50 million) may be sensitized. To characterize the scope of the P.H. problem, plant surveys and pollen sampling will be performed, initially in Texas and later in other Gulf coast areas. Vouchered samples of P.H. pollen will be collected and aqueous pollen extracts will be used for RAST testing on sera obtained in Austin and Corpus Christi, Texas (where high levels of P.H. are anticipated) from Madison, Wisconsin (where no P.H. is present), St. Louis (where occasional sensitivity is possible) and two clinics in India where sensitivity to P.H. may be a major problem and where no ragweed (a potential cross-reacting pollen) is found. Cross-reactivity of P.H. with other members of the Asteraceae will be determined initially by RAST inhibition studies, and broader studies of cross-reactivity will be done using an ELISA assay. The allergenic proteins in the P.H. pollen extract will be identified by Western blot analysis using sera positive for P.H. by RAST or ELISA analysis. Polyclonal and monoclonal antibodies raised to the allergenic proteins will be used to purify each of the proteins in sufficient quantity for skin testing patients in the U.S. gulf coast and in India. The pattern of allergenic proteins in P.H. will be compared to that found in other Asteraceae to produce a P.H. sensitivity in individuals presenting with fall seasonal pollinosis will be performed. This study including RAST, skin testing and bronchial inhalation challenge will demonstrate the true prevalence of P.H. sensitivity and correlate RAST or skin sensitivity with end organ response.